Organic electroluminescence element, display device and lighting device

ABSTRACT

In an organic electroluminescence element which incorporates a substrate having thereon an anode and a cathode and which incorporates a plurality of organic layers between the aforesaid anode and cathode, wherein at least one of the aforesaid organic layers is a first organic layer incorporating a compound having at most 10 repeating units, the first organic layer being prepared by coating the compound having at least one polymerizable group, followed by polymerization.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation application of U.S. patentapplication Ser. No. 11/817,271, filed on Aug. 28, 2007, the entirecontents of which are incorporated herein by reference and priority towhich is hereby claimed. The Ser. No. 11/817,271 is a U.S. nationalstage of application No. PCT/JP2006/302327, filed on 10 Feb. 2006, theentire contents of which are incorporated herein by reference andpriority to which is hereby claimed. Priority under 35 U.S.C. §119(a)and 35 U.S.C. §365(b) is hereby claimed from Japanese Application No.2005-057051, filed 2 Mar. 2005, the disclosure of which is alsoincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an organic electroluminescence element,a display device employing the same, and a lighting device.

BACKGROUND

Heretofore, cited as a light emitting type electronic display device hasbeen an electroluminescence display (ELD). Constituting elements of ELDinclude an inorganic electroluminescence element and an organicelectroluminescence element (hereinafter also referred to as an organicEL element).

are injected into the light emitting layer and are subjected torecombination, whereby exciton is generated. During deactivation of theresulting exciton, light (fluorescence and phosphorescence) is emitted.Light emission can be realized via application of a voltage of severalV—several tens V. Further, the organic EL element exhibits a wideviewing angle due to the self-light emitting type, and high visibility,whereby in view of space saving and portability, it has attractedattention.

For example, an EL element is known in which a thin organic film isformed via deposition of organic compounds (for example, Applied PhysicsLetters, p. 913-(1987)). The organic EL element described in the abovereference incorporates a laminated layer structure of electrontransporting materials and positive hole transporting materials, wherebyit realizes significant enhancement of light emission characteristicscompared to conventional monolayer type elements. The above laminatedlayer type element is formed via deposition of low molecular weightorganic materials as an element material.

Further disclosed is a technique in which an element is formed viadeposition of organic molecules having a repeated unit of at most 10which are prepared by polymerization of compounds having a polymerizablegroup (refer, for example, to Patent Document 1). Still furtherdisclosed is a technique in which a first layer is formed viapolymerization of compounds having a polymerizable group, andsubsequently a second layer is formed thereon via polymerization ofcompounds having a polymerizable group (refer, for example, to PatentDocument 1).

However, such forming methods employing deposition display majorproblems such as poor utilization efficiency of materials, an increasein space, and the insufficient accuracy during the production process ofthe elements.

Nature, 397 (1999) 121 describes that π electron conjugation basedpolymers such as polyparaphenylene vinylene (PPV), and derivativesthereof, may be employed as a light emitting material. Some of thesehave been employed as a clock backlight. These polymer based materialscapable of being subjected to film formation via a casting methodexhibit not only advantages in the production process but alsoadvantages in excellent durability compared to low molecular weightlight emitting materials. However, organic polymer materials whenemployed via a coating method, exhibit disadvantages such as lowsolubility in solvents and low light emission efficiency. In order toovercome these drawbacks, a method is available in which a polymerprecursor is employed and polymers are formed after coating to becomeinsoluble, whereby elution is minimized. As the above example, it ispossible to cite a method proposed by Cambridge Display Technology Co.in which PPV is employed as a precursor. The above method is detailed onpages 73—of Organic Electro-Luminescent Materials and Devices, 1997.However, since in this method, polymer structures are limited, it is notpossible to apply it to various compounds to form a light emittingelement.

Further, another method is available in which after casting employingmonomers, elution is minimized in such a manner that the monomers arepolymerized to become insoluble (refer, for example, to Patent Documents3 and 4). By employing the above methods, it becomes possible to employa laminated layer structure, whereby light emitting efficiency isimproved. However, problems have still remained in which due toinsufficient enhancement of the light emitting efficiency, dark spotstend to occur, and the life of the element is not long enough due todistortion of the boundary.

Patent Document 1: Japanese Patent Publication Open to Public Inspection(hereinafter referred to as JP-A) No. 5-247547

Patent Document 2: JP-A No. 2004-103401

Patent Document 3: JP-A No. 2003-73666

Patent Document 4: JP-A No. 2003-86377

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

In view of the foregoing, the present invention was achieved. An objectof the present invention is to provide an organic electroluminescenceelement which is structured as multiple layers, emits light at excellentlight emission efficiency, minimizes dark spots and exhibits long life,and a display device, as well as a lighting device using the same.

Means to Solve the Problems

The above object of the present invention was achieved employing thefollowing embodiments.

-   1. In an organic electroluminescence element which incorporates a    substrate having thereon an anode and a cathode and which    incorporates a plurality of organic layers between the aforesaid    anode and cathode, wherein at least one of the aforesaid organic    layers is a first organic layer incorporating a compound having at    most 10 repeating units, the first organic layer being prepared by    coating the compound having at least one polymerizable group,    followed by polymerization.-   2. The organic electroluminescence element described in 1. above,    wherein a second organic layer incorporating a compound having at    most 10 repeating units is applied onto the aforesaid first organic    layer, and then followed by polymerization, the second organic layer    being prepared by coating the compound incorporating at least one    polymerizable group onto the aforesaid first organic layer.-   3. In an organic electroluminescence element which incorporates a    substrate having thereon an anode and a cathode and which    incorporates a plurality of organic layers between the aforesaid    anode and cathode, an organic electroluminescence element, wherein a    first organic layer is formed by coating a compound having a    polymerizable group or a reactive group, followed by polymerization,    and a second organic layer is present which is formed by coating a    compound having a polymerizable group or a reactive group onto the    aforesaid fist layer, followed by polymerization, and a portion of    an interface of each of the organic layers is bonded via a covalent    bond.-   4. The organic electroluminescence element described in any one of    1.-3. above, wherein the aforesaid polymerizable group is a vinyl    group.-   5. The organic electroluminescence element described in any one of    1.-4. above, wherein the aforesaid coating is carried out employing    an ink-jet recording method.-   6. The organic electroluminescence element described in any one of    1.-5. above, wherein the aforesaid polymerization is performed via    exposure to energy rays.-   7. The organic electroluminescence element described in any one of    1.-6. above, wherein the aforesaid exposure to energy rays is    exposure to ultraviolet rays, electrons, ions, heat, radical beams,    or radioactive rays.-   8. The organic electroluminescence element described in any one of    2.-7. above, wherein the compound incorporated in the aforesaid    first organic layer is an aromatic compound having a tertiary amine    group and the compound incorporated in the aforesaid second organic    layer is a compound having an organic metal complex structure.-   9. The organic electroluminescence element described in any one of    2.-8. above, wherein the aforesaid first or second organic layer    further incorporates a phosphorescent compound.-   10. The organic electroluminescence element described in any one of    2.-9. above, wherein the aforesaid first organic layer is an    electron transporting layer and the aforesaid second organic layer    is a positive hole transporting layer.-   11. The organic electroluminescence element described in any one of    1.-10. above, wherein the aforesaid substrate is a transparent gas    barrier film.-   12. The organic electroluminescence element described in any one of    1.-11. above, wherein the emitted light is white.-   13. A display device incorporating the organic electroluminescence    element described in 12. above.-   14. A lighting device incorporating the electroluminescence element    described in 12. above.-   15. A display device incorporating the lighting device described    in 14. above and a liquid crystal element as a display means.

Effects of the Invention

Employing the present invention, it has become possible to provide amultilayered organic electroluminescence element which results in lightemission of excellent light emission efficiency, minimized dark spot,and long service life, as well as a display device and a lighting deviceusing the same.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing of the layer configuration of the gasbarrier film according to the present invention and one example of itsdensity profile.

FIG. 2 is a schematic view showing one example of an atmosphericpressure discharge treatment apparatus of a system in which a substrateis processed between counter electrodes which are applicable for thepresent invention.

FIG. 3 is a view showing discharge of organic EL element OLED1-1 of thepresent invention, and a film casting process.

FIG. 4 is a schematic view showing one example of a display devicecomposed of the organic EL element of the present invention.

FIG. 5 is a schematic view of Display Section A.

FIG. 6 is a schematic view of a lighting device.

FIG. 7 is a sectional view of a lighting device.

DESCRIPTION OF THE DESIGNATIONS

-   30 plasma discharge treatment chamber-   25 and 35 roller electrode-   36 electrode-   41 and 42 power sources-   51 gas supplying unit-   55 electrode cooling unit-   100 ITO substrate-   111 positive hole transporting layer-   112 electron transporting layer-   113 and 303 cathodes-   114 gas barrier film-   10 ink-jet system head-   D droplet-   201 display-   203 pixel-   205 scanning line-   A display section-   B control section-   302 glass cover-   306 organic EL layer-   307 glass substrate fitted with transparent electrode-   308 nitrogen gas-   309 water catching agent

BEST MODE FOR CARRYING OUT THE INVENTION

Each of the constituting requirements of the present invention will nowbe detailed.

The basic feature of the present invention is formation of an organiclayer incorporating organic molecules of a repeating unit of at most 10in such a manner that a compound (organic EL component) having at leastone polymerizable group is coated and the resulting coating is exposedto energy radiation to undergo polymerization. Further, when an organiclayer is coated thereon, a preferable embodiment is that after forming afirst organic layer, a second organic layer is formed via the sameprocess as coating of a compound having at least one polymerizable groupfollowed by polymerization. Further, the third feature is that whenlamination is carried out according to the present invention, the firstand second organic layers are partially joined via a covalent bond atthe resulting interface. An additional feature is that the organic layeris formed via a coating system, and it is specifically preferable thatthe organic layer is formed employing an ink-jet recording system.

Polymerization reaction according to the present invention may beperformed via exposure to energy radiation. Examples of such energyradiation include ultraviolet rays, electrons, ions, heat, radicalbeams, and radioactive rays. Of these, electronic energy refers to anelectric current which is supplied during driving of light emittingelements. Specifically, polymerization reaction is initiated by anionradicals of polymerizable compounds formed by electrons injected from ananode, or radical cations of polymerizable compounds formed by positiveholes injected from an anode. In addition, repeating unit, as describedin the present invention, is defined as a number average degree ofpolymerization.

In compounds having at least one polymerizable group according to thepresent invention, examples of the polymerizable groups include a vinylgroup, an epoxy group, and an oxetane group. In the present invention,by polymerizing compounds having at least one polymerizable group, it ispossible to easily prepare organic molecules having at most 10 repeatingunits in such a manner that monomers undergo polymerization underpolymerizing conditions in which reaction termination tends to occur.Listed as methods are, for example, a method to control polymerizationinitiators or catalyst concentration, a method to simultaneously employchain transfer agents or polymerization terminating agents, or a methodto control the exposure energy amount of ultraviolet rays, electrons,ions, heat, radical beams or radioactive rays.

Examples of radical polymerization initiators employed in the presentinvention include azo based initiators such as 2,2′-azobisbutyronitrile,2,2′azobiscyclohexanecarbonitrile,1,1′-azobis(cyclohexane-1-carbonitrile,2,2′-azobis(2-methylbytyronitrile),2,2′-azobis(2,4-dimethylvaleronitrile),2,2′azobis(4-methoxy-2,4-dimethylvaleronitrile),4,4′-azobis(4-cyanovaleric acid), 2,2′-azobisisobutyric acid dimethyl,2,2′-azobis(2-methylpropionamidooxime),2,2′-azobis(2-(2-imidazoline-2-yl)propane), or2,2′-azobis(2,4,4-trimethylpentane); peroxide based initiators such asbenzoyl peroxide, di-t-butyl peroxide, t-butylhydro peroxide, orcumenehydro peroxide; aromatic carbonyl based initiators such asdiethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1-one,benzyldimethylketal, benzyl-β-methoxyethylacetal,1-(4-isopropylphenyl-2-hydroxy-2-methylpropane-1-one,4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone,1-hydroxycyclohexyl phenyl ketone, 4-phenoxydichloroacetophenone,4-t-butyldichloroacetophenone, 4-t-butyltrochloroacetophenone, or1-(4-dodecylphenyl)-2-hydroxy-2-methylpropane-1-one. Further employedmay be disulfide based initiators such as tetraethylthiirane disulfide,nitroxyl initiators such as 2,2,6,6-tetramethylpyperidine-1-oxyl, andliving radical polymerization initiators such as a4,4′-di-butyl-2,2′-bipyridine copper complex-methyl trichloroacetatecomposite.

Examples of acid catalysts, which are employed in the present invention,include clay such as active clay or acid clay; mineral acids such assulfuric acid or hydrochloric acid; organic acids such asp-toluenesulfonic acid, or trifluoroacetic acid; Lewis acids such asaluminum chloride, ferric chloride, stannic chloride, titaniumtrichloride, titanium tetrachloride, boron trifluoride, hydrogenfluoride, boron tribromide, aluminum bromide, gallium chloride, orgallium bromide; and further solid acids such as zeolite, silica,alumina, silica-alumina, cation exchange resins, or heteropoly acids(for example, phosphorous tungstic acid, phosphorous molybdic acid,silicotungstic acid, and silicomolybdic acid.

Cited as basic catalysts which are employed in the present inventionmay, for example, be alkaline metal carbonates such as Li₂O₃, Na₂CO₃, orK₂CO₃; alkaline earth metal carbonates such as BaCO₃ or CaCO₃; alkalinemetal oxides such as LiO₂, Na₂O, or K₂O; alkaline earth metal oxidessuch as BaO or CaO; alkaline metals such as Na or K; alkaline metalhydroxides such as sodium hydroxide or potassium hydroxide; andalkoxides of sodium, potassium, rubidium and cesium.

In the present invention, it is possible to control the molecular weightof the resulting oligomer depending on the used amount of polymerizationinitiators or catalysts. Namely, when the used amount of thepolymerization initiators or catalysts increases with respect tocompounds having at least one polymerizable group, which are monomers,the molecular weight of the resulting oligomer decreases. The usedamount of the polymerization initiators or catalysts is commonly in therange of 0.1-100% by weight with respect to the compound having at leastone polymerizable group, but is preferably in the range of 1-20% byweight.

Employed as a chain transfer agent or a polymerization terminating agentmay, for example, be acids such as hydrochloric acid, sulfuric acid, oracetic acid, polyhalogenated methane, halogenated hydrocarbon,mercaptans, α-methylstyrene dimers, active hydrogen compounds such asalcohol, 2,2-disubstituted olefin such as2,4-diphenyl-4-methyl-1-pentane, and transition metal complexes such ascobalt complexes. The used amount of the chain transfer agents andpolymerization terminating agents is preferably 0.01-0.5 in terms of molratio with respect to the compound having at least one polymerizablegroup.

Specific examples of compounds having at least one polymerizable groupwill now be listed; however, the present invention is not limitedthereto.

In cases in which compounds are employed, which have a polymerizablegroup or a reactive group, according to the present invention, a featureis that some of the interfaces of each of the organic layers are joinedvia a covalent bond. Specifically, it is essential that conditions arerealized so that the interface formed between the first organic layerand the second organic layer, each of which functions differently, isjoined via a bond such as a covalent bond. In order to realize theabove, it is preferable that compounds having self-polymerizable groups,such as a vinyl group or an epoxy group, are employed to constitute eachof the first and second organic layers, or a compound having a reactivegroup, listed in following Group I, is employed in the first organiclayer, while a compound having a reactive group, listed in followingGroup II, are employed in the second organic layer.

Of combinations of the above reactive groups, preferred is a combinationcapable of undergoing addition reaction without formation of H₂O.

Compounds having a polymerizable group or a reactive group according tothe present invention, as described herein, refer to compounds capableof forming polymers in such a way that single compounds react with eachother or compounds capable of forming a covalent bond in such a mannerthat two differing compounds reacts with each other. Preferred compoundsinclude those which result in no release of molecules duringpolymerization reaction, or compounds having a functional group such asan epoxy group capable of undergoing ring-opening polymerization, butthe most preferred compounds include those having a vinyl group.

In the present invention, to enhance performance of the element, it ispreferable that the function of the first organic layer differs fromthat of the second organic layer. Further, it is preferable that thepositive hole transporting materials, and electron transportingmaterials described below, as well as the structure listed as an exampleof the light emitting layer, are provided individually.

The compounds which are employed in the first organic layer or thesecond organic layer are preferably either of the compounds having anaromatic tertiary amine structure or an organic metal complex structure.However, it is more preferable that the compounds employed in the firstorganic layer have an aromatic tertiary amine structure and thecompounds employed in the second organic layer have an organic metalcomplex structure.

Examples of compounds having a polymerizable group or a reactive groupwill now be listed, however, the present invention is not limitedthereto.

The compounds according to the present invention are incorporated as amajor component in at least two organic layers constituting the organicEL element of the present invention, but other appropriate compounds maybe incorporated.

In the organic EL element of the present invention, it is preferablethat coating (formation) of each of the above organic layers representedby the first or second organic layer is carried out via an ink-jetrecording systems.

An ink-jet recording apparatus applicable to the present invention isconstituted of an energy generating means to discharge a solutionincorporating compounds having at least one polymerizable group to formthe organic layer according to the present invention, an ink-jet headprovided with nozzles to discharge the above solution, an electriccircuit to provide signals to drive the ink-jet head, an insufficientdischarge recovering means (also called a maintenance means) to securestable discharge of the above solution incorporating compounds having atleast one polymerizable group, and a capping means to cover the nozzlesurface employing a capping member so that the above solution is notsolidified due to evaporation when the ink-jet head is in the standbymode during non-use periods.

Listed as discharge systems of the employed ink-jet head are anelectrical-mechanical conversion system (for example, a single-cavitytype, a double-cavity type, a vendor type, a piston type, a share modetype, and a shared wall type), an electrical-thermal conversion system(for example, a thermal ink-jet type, and a BUBBLE INK-JET (being aregistered trade mark) type, an electrostatic attracting system (forexample, an electric field controlling type, and a slit-jet type), andan electric discharge type (for example, a spark-jet type). Of these,preferred is the electrical-mechanical conversion system, but any ofthem are employable.

Further, it is preferable that in the organic EL element of the presentinvention, after coating (forming) each of the organic layersrepresented by the first or second organic layer according to thepresent invention, polymerization is performed via exposure to energyrays, which are preferably any of the ultraviolet rays, electrons, ions,heat, radical beams and radioactive rays. Employed as an ultraviolet raysource may be mercury lamps, metal halide lamps, excimer lamps, andultraviolet ray laser-LEDs. Further, an electron beam exposure apparatusis detailed in “UV-EB Koka Gijutu no Tenkai (Development of UV-EB CuringTechnology)” (edited by Radotech Kenkyu Kai, published by CMC Co., page95 1999). Recently, a down-sized electron beam exposure apparatus hasbeen introduced in Toso Gijutsu, October 2001, page 90. The electronbeam exposure apparatus employed in the present invention is notparticularly limited, but as an electron beam accelerator for such anelectron beam exposure, commonly, a curtain beam system apparatus iseffectively employed which is relatively inexpensive and results inrelatively high output. During exposure to electron beams, accelerationvoltage is preferably 100-300 kV, while the absorption dose ispreferably 0.5-10 Mrad.

The organic EL element of the present invention will now be described.

Examples of compounds incorporated in the organic EL element of thepresent invention include fluorescent compounds and phosphorescentcompounds, whereby light emission of the organic EL element is realizedvia incorporated fluorescent or phosphorescent compounds. Preferred asthe fluorescent compounds are those of a high quantum yield employed inlaser dyes. Further, in recent years, an organic EL element employingphosphorescent emission from an excited triplet state is reported fromPrinceton University (M. A. Baldo et al., Nature, Volume 395, pages151-154 (1998)), which receives attention, since the light emissionefficiency is basically greater by a factor of 4, compared to theorganic EL element employing fluorescent emission from an excitedsinglet state. In the present invention, in terms of light emissionefficiency, incorporation of phosphorescent compounds is preferred.

Preferred fluorescent compounds are those which exhibit a highfluorescence quantum yield in the solution state, wherein fluorescencequantum yield is preferably at least 10%, but is more preferably atleast 30%. Specific fluorescent compounds include coumarin based dyes,pyran based dyes, cyanine based dyes, croconium based dyes, squaryliumbased dyes, oxobenzanthracene based dyes, fluorescein based dyes,rhodamine based dyes, pyrylium based dyes, perylene based dyes, stilbenebased dyes, polythiophene based dyes, and rare earth metal complex basedphosphors. It is possible to determine the fluorescence quantum yieldemploying the method described on page 362 of Bunko II of Dai 4 HanJikken Kagaku Koza (4th Edition, Lectures of Experimental Chemistry)(1992 Edition, Maruzen).

Phosphorescent compounds, as described in the present invention, arethose which are observed for light emission from an excited tripletstate and which result in a phosphorescence quantum yield of at least0.001 at 25° C. The phosphorescence quantum yield is preferably at least0.01, but is more preferably at least 0.1. It is possible to determinethe above phosphorescence quantum yield employing the method describedon page 398 of Bunko II of Dai 4 Han Jikken Kagaku Koza (4th Edition,Lectures of Experimental Chemistry) (1992 Edition, Maruzen).Phosphorescent compounds may be employed in the present invention if theabove phosphorescence quantum yield is realized in any of theappropriate solvents.

Phosphorescent compounds employed in the present invention arepreferably complex based compounds incorporating any of the Group IIImetals in the periodic table. More preferred compounds include iridiumcompounds, osmium compounds, or platinum compounds (being platinumcomplex based compounds), and of these, the iridium compounds are mostpreferred.

Specific examples of the phosphorescent compounds employed in thepresent invention will now be listed; however the present invention isnot limited thereto. It is possible to synthesize these compoundsemploying the methods, for example, described in Inorg. Chem., Volume40, 1704-1711. Further, fluorescent and phosphorescent compounds mayincorporate either a polymerizable group or a reactive group.

The layer configuration of the organic electroluminescence element(being the organic EL element) of the present invention will now bedescribed.

The light emitting layer according to the present invention refers, in abroad sense, to the layer which emits light when an electric current ispassed through electrodes composed of a cathode and an anode andspecifically refers to the layer incorporating compounds which emitlight when passing through the electrodes composed of a cathode and ananode.

If desired, the organic EL element of the present inventionincorporates, other than the light emitting layer, a positive holetransporting layer, an electron transporting layer, an anode bufferlayer, and a cathode buffer layer, which are sandwiched between thecathode and anode. Specifically, the following structures are listed.

-   (i) anode/positive hole transporting layer/light emitting    layer/cathode-   (ii) anode/light emitting layer/electron transporting layer/cathode-   (iii) anode/positive hole transporting layer/light emitting    layer/electron transporting layer/cathode-   (iv) anode/anode buffer layer/positive hole transporting layer/light    emitting layer/electron transporting layer/cathode buffer    layer/cathode

It is preferable that of a plurality of layers sandwiched between theelectrodes (namely the anode and the cathode) which constitutes theabove organic EL element, at least two adjacent layers are constitutedof the first organic layer incorporating a first compound according tothe present invention, and the second organic layer incorporating asecond compound according to the present invention. Further, it ispreferable to incorporate at least three organic layers between thecathode and the anode.

<<Light Emitting Layer>>

The light emitting layer related to the organic EL element of thepresent invention will now be described. The light emitting layer is theone which emits light via recombination of electrons and positive holeswhich are injected from the electrodes, the electron transporting layer,or the positive hole transporting layer, and light emitting portions maybe within the light emitting layer or at the interface between the lightemitting layer and the adjacent layer.

It is preferable that materials employed in the light emitting layer(hereinafter referred to as light emitting materials) are organiccompounds or complexes which fluoresce or phosphoresce. Usable materialsmay be appropriately selected from those known in the art, which areemployed in the light emitting layer of the organic EL element. Most ofsuch light emitting materials are organic compounds, and it is possibleto employ those described, for example, in Macromol. Synth. Volume 125,pages 17-25 depending on desired color tone.

In the organic EL element of the present invention, light emittingmaterials may simultaneously exhibit, other than light emittingperformance, a positive hole transporting function and an electrontransporting function, whereby it is possible to employ almost anypositive hole transporting material and electron transporting materialas a light emitting material. Light emitting materials may be polymermaterials such as p-polyphenylnene vinylene or polyfluorene, andfurther, employed may be polymer materials in which the above lightemitting materials are introduced into a polymer chain or the abovelight emitting materials are employed as a main chain of the polymer.

Generally, in terms of performance of the elements, it is preferable toarrange the light emitting layer on the cathode side rather than in thepositive hole transporting layer. Accordingly, compared to positive holetransporting materials, all materials employed in the light emittinglayer relatively become electron transporting materials (under thedefinition of the present invention).

(Thickness of Light Emitting Layer)

Thickness of the light emitting layer, prepared as above is notparticularly limited and appropriate ones may be chosen depending on thesituation. However, it is preferable to control the thickness in therange of 5 nm-5 μm.

Described now will be other layers, which constitute the organic ELelement in combination with light emitting layers such as a positivehole injecting layer, a positive hole transporting layer, an electroninjecting layer, or an electron transporting layer. <<Positive HoleInjecting Layer, Positive Hole Transporting Layer, Electron InjectingLayer, and Electron Transporting Layer>>

The positive hole injecting layer and the positive hole transportinglayer employed in the present invention exhibit the function in whichthe positive holes injected from an anode are transferred to the lightemitting layer. By arranging the above positive hole injecting layer andpositive hole transporting layer between the anode and the lightemitting layer, many positive holes are injected into the light emittinglayer in a lower electric field, and further, electrons, which areinjected into the light emitting layer from the cathode, the electroninjecting layer or the electron transporting layer, are accumulated atthe interface within the light emitting layer, due to the electron wallwhich exists at the interface between the light emitting layer and thepositive hole injecting layer or the positive hole transporting layer,whereby an element exhibiting excellent light emitting performance suchas enhanced light emitting efficiency is produced.

<<Positive Hole Injecting Materials and Positive Hole TransportingMaterials>>

Materials of the positive hole injecting layer and positive holetransporting layer (hereinafter referred to as positive hole injectingmaterial and positive hole transporting materials) are not particularlylimited as long as they transport positive holes injected from the aboveanode to the light emitting layer. It is possible to employ anyappropriate ones selected from those which are commonly employed aspositive hole injecting transporting materials in photoconductivematerials and which are conventionally employed in the positive holeinjecting layer and the positive hole transporting layer in organic ELelements.

The above positive hole injecting materials and positive holetransporting materials exhibit any of the injection or transport ofpositive holes, or a barrier against electrons, and may be eitherorganic or inorganic materials. Examples of the above positive holeinjecting materials and positive hole transporting materials includetriazole derivatives, oxadiazole derivatives, imidazole derivatives,polyarylalkane derivatives, pyrazoline derivatives, pyrazolonederivatives, phenylenediamine derivatives, arylamine derivatives,amino-substituted chalcone derivatives, oxazole derivatives,styrylanthracene derivatives, fluorenone derivatives, hydrazonederivatives, stilbene derivatives, and silazane derivatives, as well asaniline based copolymers, and conductive polymer oligomers, especiallythiophene oligomer.

It is possible to employ those materials described above as a positivehole injecting material and a positive hole transporting material.However, it is preferable to employ porphyrin compounds, aromatictertiary amine compounds, styrylamine compounds, and it is particularlypreferable to employ the aromatic tertiary amine compounds.

Typical examples of the above aromatic tertiary amine compounds andstyrylamine compounds include N,N,N′,N′-tetraphenyl-4,4′-diaminophenyl,N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine(TPD), 2,2-bis(4-di-p-tolylaminophenyl)propane,1,1-bis(4-di-p-tolylaminophenyl)cyclohexane,N,N,N′,N′-tetra-p-tolyl-4,4′-diaminobiphenyl,1,1-bis(4-di-p-tolylaminophenyl)-4-phenylcyclohexane,bis(4-dimethylamino-2-methylphenyl)phenylmethane,bis(4-di-p-tolylaminophenol)phenylmethane,N,N′-diphenyl-N,N′-di(4-methoxyphenyl)-4,4′diaminobiphenyl,N,N,N′,N′-tetraphenyl-4,4′-diaminodiphenyl ether,4,4′-bis(diphenylamino)quodriphenyl, N,N,N-trip-tolyl)amine,4-(di-p-tolylamino)-4′-[4-(di-p-tolylamino)styryl]stilbene,4-N,N-diphenylamino-(2-diphenylvinyl)benzene,3-methoxy-4′-N,N-diphenylaminostyrylbenzene, and N-phenylcarbazole, aswell as those having two condensed aromatic rings in the molecule,described in U.S. Pat. No. 5,061,569, such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (α-NPD), and4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (MTDATA)described in JP-A No. 4-308688, in which three triphenylamine units areconnected in a star burst type. Further, it is possible to employpolymer materials in which any of the above materials are introduced inpolymer chains or are employed as a principal chain of the polymer.

Alternatively, it is possible to employ inorganic compounds such as ptype-Si or p type-SiC as a positive hole injecting material or apositive hole transporting material. It is also possible to form theabove positive hole injecting layer and positive hole transporting layerin such a manner that the above positive hole injecting materials andpositive hole transporting materials are formed as a thin film,employing the methods known in the art, such as a vacuum depositionmethod, a spin coating method, a casting method, or the LB method.

(Thickness of Positive Hole Injecting Layer and Thickness of PositiveHole Transporting Layer)

The thickness of positive hole injecting layers and positive holetransporting layers is not particularly limited, but is preferably inthe range of 5 nm-5 μm. The above positive hole injecting layer orpositive hole transporting layer may be constituted of a single layercomposed of at least one of the above materials, or of a multilayercomposed of a plurality of layers, each of which is composed of the sameor a differing composition. <<Electron Transporting Layer and ElectronTransporting Materials>>

The electron transporting layer according to the present invention mayexhibit a function in which electrons injected from a cathode aretransferred to a light emitting layer. Any of the appropriate materialsare selected from those known in the art and employed.

Examples of materials employed in the above electron transporting layer(hereinafter referred to as electron transporting materials) includenitro-substituted fluorene derivatives, diphenylquinone derivatives,thiopyran dioxide derivatives, heterocyclic tetracarboxylic anhydrides,carbodiimide, fluorenylidenemethane derivatives, anthraquinodimethaneand anthrone derivatives, and oxadiazole derivatives, as well as organicmetal complexes. Further employed as an electron transporting materialmay be thiadiazole derivatives which are prepared in such a manner thatthe oxygen atom of the oxadiazole ring of the above oxadiazolederivatives is substituted with a sulfur atom and quinoxalinederivatives having a quinoxaline ring known as an electron attractivegroup. Further, it is possible to employ polymer materials which areprepared by introducing these materials into the polymer chain or byemploying these materials as the principal chain.

Further, employed as an electron transporting material may be metalcomplexes of 8-quinolinol derivatives such astris(8-quinolinol)aluminum, tris(5,7-dichloro-8-quinilinol)aluminum,tris(5,7-dibromo-8-quinolinol)aluminum,tris(2-methyl-8-quinolinol)aluminum,tris(5-methyl-8-quinolinol)aluminum, and bis(8-quinolinol)zinc (Znq), aswell as metal complexes in which the center metal of these metalcomplexes is replaced with In, Mg, Cu, Ca, Sn, Ga or Pb.

Other than the above, preferably employed as an electron transportingmaterial may be metal-free or metal phthalocyanines, and those which areprepared by substituting the terminal of the above compound with analkyl group or a sulfonic acid group. Further employed as an electrontransporting material may be distyrylpyrazine derivatives, exemplifiedas the material of the light emitting layer, and employed as an electrontransporting material may be n type-Si and n type-SiC in the same manneras for the positive hole injecting layer and the positive holetransporting layer.

(Thickness of Electron Transporting Layer)

The thickness of the electron transporting layer is not particularlylimited, and it is preferable to prepare the above layer so that theresulting thickness is in the range of 5 nm-5 μm. The above electrontransporting layer may be constituted of a single layer composed of atleast one of the above materials or of a multilayer composed of aplurality of layers each of which is composed of the same or differentcomposition.

Further, in the present invention, incorporation of fluorescentcompounds is not limited to the light emitting layer. At least onefluorescent compound having the maximum fluorescence wavelength in thesame region as that of the fluorescent compound, which becomes the hostcompound of the above phosphorescent compound, may be incorporated inthe positive hole transporting layer or the electron transporting layeradjacent to the light emitting layer. By doing so, it is possible tofurther enhance the light emission efficiency of EL elements. Themaximum fluorescence wavelength of these fluorescent compoundsincorporated in the positive hole transporting layer and the electrontransporting layer is preferably 350-440 nm, but is more preferably390-410 nm, which is the same as for those incorporated in the lightemitting layer.

Examples which are suitable for preparing the organic EL element of thepresent invention will now be described. As an example, described is thepreparation method of an EL element structured as the above-citedanode/positive hole injecting layer/positive hole transportinglayer/light emitting layer/electron transporting layer/electroninjecting layer/cathode.

Initially, an anode is prepared in such a manner that a thin film of atmost 1 μm but preferably 10-200 nm, composed of desired electrodematerials is formed on an appropriate substrate, employing a method suchas deposition or sputtering. Subsequently, formed on the resulting anodeis a thin film composed of a positive hole injecting layer, a positivehole transporting layer, a light emitting layer, an electrontransporting layer/an electron injecting layer. Further, between theanode and the light emitting layer or the positive hole injecting layer,and between the cathode and the light emitting layer or the electroninjecting layer, may be a buffer layer (being an organic interfacelayer).

The buffer layer, as described herein, refers to the layer arrangedbetween the electrode and the organic layer for a decrease in drivingvoltage and enhancement in light emission efficiency. Buffer layers aredetailed in Chapter 2 “Denkyoku Zaioryo (Electode Materials)” (pages123-166) of Part 2 of “Yuuki EL Soshi to Sono Kogyoka Saizensen(Industrialization Front of Organic EL elements)”, published by NTN Co.,Nov. 30, 1998) and include an anode buffer layer and a cathode bufferlayer.

The anode buffer layer is also detailed in JP-A Nos. 9-45479, 9-260062,and 8-288069, and specific examples include a phthalocyanine bufferlayer represented by copper phthalocyanine, an oxide buffer layerrepresented by vanadium oxide, and a polymer buffer layer employingconductive polymers such as polyaniline (emraldine) or polythiophene.

The cathode buffer layer is also detailed in JP-A Nos. 6-325871,9-17574, and 10-74586, and specific examples of which include a metalbuffer layer represented by strontium and aluminum, an alkaline earthmetal compound buffer layer represented by lithium fluoride, an alkalineearth metal compound buffer layer represented by magnesium fluoride, andan oxide buffer layer represented by aluminum oxide or lithium oxide.

It is preferable that the above buffer layer is structured as anextremely thin film. Though depending on components, its thickness ispreferably in the range of 0.1-100 nm.

Further, other than the above basic constituting layers, if necessary,laminated may be layers exhibiting other functions. For example,incorporated may be functional layers such as the positive hole blocking(hole blocking) layer described in JP-A Nos. 11-204258 and 11-204359, aswell as on page 237 of “Yuuki EL Soshi to Sono Kogyoka Saizensen(Industrialization Front of Organic EL elements)”.

<<Electrodes>>

Electrodes of the organic EL element of the present invention will nowbe described. The electrodes of the organic EL element are composed of acathode and an anode. Preferably employed as the anode in the organic ELelement of the present invention are those in which metals of arelatively high work function (at least 4 eV), alloys, electricallyconductive compounds and mixtures thereof are employed as an electrodematerial. Specific examples of such electrode materials include metalssuch as Au, and transparent electrically conductive materials such asCuI, indium tin oxide (ITO), SfO₂, or ZnO.

The above anode may be formed in such a manner that a thin film of theabove electrode materials is formed via deposition or sputtering andthen a pattern in the desired shape is formed via photolithography.Alternatively, in cases in which high accuracy of a pattern is notneeded (approximately at least 100 μm), a pattern may be formed via amask in the desired shape during deposition or sputtering of the aboveelectrode materials. When light emission is realized from the aboveanode, it is preferable that the resulting transmittance is regulated tobe at least 10%, or the sheet resistance as an anode is preferably atmost several hundreds Ω/□. Further, though depending on materials, theselected film thickness is commonly in the range of 10 nm-1 μm, but ispreferably in the range of 10-200 nm.

On the other hand, preferably employed as the cathode are metals of arelative low work function (at most 4 eV) (called electron injectingmetals), alloys, electrically conductive compounds, and the mixturesthereof. Specific examples of such electrode materials include sodium,sodium-potassium alloy, magnesium, lithium, magnesium/copper mixtures,magnesium/silver mixtures, magnesium/aluminum mixtures, magnesium/indiummixtures, aluminum/aluminum oxide (Al₂O₃) mixtures, indium,lithium/aluminum mixtures, and rare earth metals. Of these, in view ofelectron injection properties and resistance against oxidation,appropriate are mixtures of electron injecting metals and other metalswhich exhibit larger value of the work function than the above metal andare stable, such as a magnesium/silver mixture, a magnesium/aluminummixture, a magnesium/indium mixture, an aluminum/aluminum oxide (Al₂O₃)mixture, or a lithium/aluminum mixture.

It is possible to form the thin film of the above cathode employing theabove electrode materials via a method such as deposition or sputtering.Further, sheet resistance as the cathode is preferably at most severalhundreds Ω/□, while the film thickness is commonly in the range of 10nm-1 μm, but is preferably in the range of 50-200 nm. In order totransmit emitted light, it is advantageous that either the anode or thecathode, which is the organic EL element of the present invention, istransparent or translucent, since light emission efficiency is enhanced.

<<Display Device>>

The organic EL element may be employed as a kind of lamp, used forlighting or as an exposure light source, or as a display of a type suchas a projection apparatus which projects images, or a type in whichstill images or moving images are directly viewed. When employed as adisplay device to reproduce moving images, the driving system may beeither a simple matrix (being a passive matrix) system or an activematrix system. By employing at least two organic EL elements of thepresent invention, which exhibit different colors of emitted light, itis possible to prepare a full color display device.

<<Light Extracting Technology>>

In order to enhance light extracting efficiency of light emitted fromthe light emitting layer, in the organic El element of the presentinvention, the surface of the substrate may be subjected to prism orlens-like machining, or a prism sheet and a lens sheet may be adhered tothe surface of the substrate.

The organic EL element of the present invention may incorporate a lowrefractive index layer between the transparent electrode and thetransparent substrate. A low refractive index layer may be composed ofmaterials such as aerogel, porous silica, magnesium fluoride, andfluorine based polymers.

The refractive index of the transparent substrate is commonly about1.5-about 1.7. Consequently, the refractive index of the low refractiveindex layer is preferably at most 1.5, but is more preferably at most1.35. Further, the thickness of the low refractive index medium ispreferably twice of the wavelength in the medium. The reason for this isthat when the thickness of the low refractive index medium reachesapproximately the wavelength of light in which electromagnetic wavesexuded via evanescent enters into the substrate, effects of the lowrefractive index layer decrease.

The organic EL element of the present invention may have a diffractiongrating between any of the layers or in the media (in the transparentsubstrate and the transparent electrode). It is preferable that theintroduced diffraction grating exhibits a two-dimensional periodicrefractive index. The reason for this is that since light emitted fromthe light emitting layer travels randomly in all directions, in a commonone-dimensional diffraction grating, light which travels in thespecified direction is only diffracted, whereby light extractingefficiency is not markedly enhanced. However, by converting therefractive index distribution to a two-dimensional distribution, lightwhich travels in any direction is diffracted, whereby the lightextracting efficiency increases. As noted above, the position forintroduction of the diffraction grating may be between any of the layersor in the media (in the transparent substrate and in the transparentelectrode). However, positions near the organic light emitting layer,where light is generated, is preferred. In such a case, the period ofdiffraction grating is preferably about ½—three times that of thewavelength of light in the medium. Arrangement of the diffractiongrating is preferably repetition of two-dimensional arrangement such asa square lattice, a triangular lattice or a honeycomb lattice.

<<Gas Barrier Layer>>

In the organic EL element of the present invention, it is preferablethat the substrate is a transparent gas barrier film having thereon agas barrier layer. The composition of the gas barrier layer according tothe present invention is not particularly limited as long as the layerinhibits transmission of oxygen and moisture. Specific materialsconstituting the gas barrier layer according to the present inventionare preferably inorganic oxides, which may include silicon oxide,aluminum oxide, silicon oxide nitride, aluminum oxide nitride, magnesiumoxide, zinc oxide, indium oxide, and tin oxide.

Further, the thickness of the gas barrier layer is appropriatelyselected though optimum conditions differ depending the type ofmaterials used and their configuration, but is preferably in the rangeof 5-2,000 nm. When the thickness of the gas barrier layer is less thanthe above lower limit, it is not possible to prepare a uniform filmwhereby it becomes difficult to realize barring properties againstgases. On the other hand, when the thickness of the gas barrier layerexceeds the above upper limit, it becomes difficult to maintainflexibility of the gas barrier film, whereby the gas barrier film maycrack due to external factors such as folding and pulling after casting.

It is possible to form the gas barrier layer according to the presentinvention in such a manner that the raw materials, described below, areapplied onto a substrate such as a flexible transparent film, employinga spray method, a spin coating method, a sputtering method, an ionassist method, and a plasma CVD method, described below, as well as theplasma CVD method under atmospheric pressure or pressure nearatmospheric pressure, also described below.

However, in wet processes such as a spray method or a spin coatingmethod, it is difficult to realize flatness at the molecular level(being the nm level). Further, since solvents are employed, a drawbackresults in which usable substrates or solvents are limited due to thefact that the substrates, described below, are organic materials.Consequently, in the present invention, those which are formed via theplasma CVD method are preferred. The atmospheric pressure plasma CVDmethod is particularly preferred since it requires no vacuum chamber andis a high productive casting method capable of achieving high ratecasting. By forming the above barrier layer via the atmospheric pressureplasma CVD method, it becomes possible to easily form a uniform filmexhibiting surface flatness.

In regard to the plasma CVD method or a plasma CVD method under anatmospheric pressure or pressure near the atmospheric pressure, it isparticularly preferred that formation is carried out employing the CVDplasma method under an atmospheric pressure or a pressure near theatmospheric pressure. Layer forming conditions of the plasma CVD methodwill now be detailed.

A gas barrier layer is preferred which is prepared via the plasma CVDmethod or the plasma CVD method under an atmospheric pressure or apressure near the atmospheric pressure for the following reasons. Bychoosing conditions such as organic metal compounds as a raw material,decomposition gas, decomposition temperature, or applied electric power,it is possible to selectively prepare any of the metal carbides, metalnitrides, metal oxides, metal sulfides, and metal halides, as well asmixtures thereof (such as metal oxide nitrides, metal oxide halides, ormetal nitride carbides).

For example, silicon oxide is prepared by employing a silicon compoundas a raw material and oxygen as a decomposition gas, while zinc sulfideis prepared by employing a zinc compound as a raw material and carbondisulfide gas as a decomposition gas. The reason for this is as follows.In a plasma space, very active charged particles and active radicals arepresent at high concentration, whereby multi-staged chemical reaction isaccelerated at a high rate and elements existing in the plasma space areconverted to thermodynamically stable compounds within a very shortperiod.

Raw materials of the above inorganic compounds may be in any state ofgas, liquid, or solid at normal temperature and normal pressure whenincorporating transition metal elements. In the case of gas, it may beintroduced into a discharge without any modification. In the case ofliquid or solid, they are employable upon being vaporized employingmeans such as heating, bubbling, reduced pressure, or exposure toultrasonic waves. Further, they may be employed upon being diluted withsolvents. Usable solvents include organic solvents such as methanol,ethanol, n-hexane, or mixed solvents thereof. Further, these dilutionsolvents are subjected to decomposition to molecules or atoms duringplasma discharge treatment, whereby their effects are negligible.

Organic metal compounds such as above include silicon compounds such assilane, tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane,tetraisoproxysilane, tetra-n-butoxysilane, tetra-t-butoxysilnae,dimethyldimethoxysilane, dimethyldiethoxysilane,dimethyldimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane,ethyltrimethoxysilane, phenyltriethoxysilane,(3,3,3-trifluoropropyl)trimethoxysilane, hexamethyldisiloxane,bis(dimethylamino)dimethylsilane, bis(dimethylamino)methylvinylsilane,bis(ethylamino)dimethylsilane, N,O-bis(trimethylsilyl)acetamide,bis(trimethylsilyl)carboidiimide, diethylaminotrimethylsilane,dimethylaminodimethylsilane, hexamethyldisilazane,hexamethylcyclotrisilazane, heptamethyldisilazane,nanomethyltrisilazane, octamethylcyclotetrasilazane,tetrakisdimethylaminosilane, tetraisocyanatosilane,tetramethyldisilazane, tris(dimethylamino)silane, triethoxyfluorosilane,allyldimethylsilane, allyltrimethylsilane, benzyltrimethylsilane,bis(trimethylsilyl)acetylene, 1,4-bistrimethylsilyl-1,3-butadine,di-t-butylsilane, 1,3-disilabutane, bis(trimethylsilyl)methane,cyclopentadienyltrimethylsilane, phenyldimethylsilane,phenyltrimethylsilane, propalgyltrimethylsilane, tetramethylsilane,trimethylsilylacetylene, 1-(trimethylsilyl)-1-propine,tris(trimethylsilyl)methane, tris(trimethylsilyl)silane,vinyltrimethylsilane, hexamethyldisilane, octamethylcyclotetrasiloxane,tetramethylcyclotetrasiloxane, hexamethylcyclotetrasiloxane, and MSILICATE 51.

Examples of titanium compounds include titanium methoxide, titaniumethoxide, titanium isoproxide, titanium tetraisoporopoxide, titaniumn-butoxide, titanium diisopropoxydo(bis-2,4-pentandionate), titaniumdiisopropoxydo(bis-2,4-ethylacetate), titaniumdi-n-butoxyd(bis-2,4-pentanedionate), titanium acetylacetate, and butyltitanate dimers.

Examples of zirconium compounds include zirconium n-propoxide, zirconiumn-butoxide, zirconium t-butoxide, zirconiumtri-n-butoxydoacetylacetonate, zirconiumdi-n-butoxydobisacetylacetonate, zirconium acetylacetonate, zirconiumacetate, and zirconium hexafluoropentanedionate.

Examples of aluminum compounds include aluminum ethoxide, aluminumtriisopropoxide, aluminum isopropoxide, aluminum n-butoxide, aluminums-butoxide, aluminum t-butoxide, aluminum acetylacetonate, andtriethyldialuminum tri-s-butoxide.

Examples of boron compounds include diborane, tetraborane, boronfluoride, boron chloride, boron bromide, borane-diethyl ether complexes,borane-THF complexes, borane-dimethylsulfide complexes, borontrifluoride diethyl ether complexes, triethylborane, trimethoxyborane,triethoxyborane, tri(isopropoxy)borane, borazol, trimethylborazol,triethylborazol, and triisopropylborazol.

Examples of tin compounds include tetraethyltin, tetramethyltin,di-n-butyltin diacetate, tetrabutyltin, tetraoctyltin, tetraethoxytin,methyltriethoxytin, diethyldiethoxytin, triisopropylethoxytin,diethyltin, diisoproipyltin, dibutyltin, diethoxytin, dimethoxytin,diisopropoxytin, dibutoxytin, tin dibutylate, tin diacetacetonate,ethyltin acetacetonate, ethoxytin acetacetonate, dimethyltindiacetacetonate, tin hydride compounds, and tin halides such as tindichloride or tin tetrachloride.

Further, examples of other organic metal compounds include antimonyethoxide, arsenic triethoxide, barium 2,2,6,6-teramethylheptanedionate,beryllium acetylacetonate, bismuth hexafluoropentanedionate,dimethylcadmium, calcium 2,2,6,6-tetramethylheptanedionate, chromiumtrifluotopentanedionate, cobalt acetylacetonate, copperhexafluoropentanedionate, magnesium hexafluoropentanedionate-dimethylether complexes, gallium ethoxide, tetraethoxygermane,tetramethoxygermane, hafnium t-butoxide, hafnium ethoxide, indiumacetylacetonate, indium 2,6-dimethylaminoheptanedionate, ferrocene,lanthanum isoproxide, lead acetate, tetraethyllead, neodymiumacetylacetonate, platinum hexafluoropentanedionate,trimethylcyclopentadienylplatinum, rhodium cabonylacetylacetonate,strontium 2,2,6,6-tetramethylheptanedionate, tantalum methoxide,tantalum trifluoroethoxide, tellurium ethoxide, tungsten ethoxide,vanadium triisopropoxydoxide, magnesium hexafluoroacetylacetonate, zincacetylacetonate, and diethylzinc.

Further, examples of decomposition gases, which decompose raw materialgas incorporating those metals to prepare inorganic compounds, includehydrogen gas, methane gas, acetylene gas, carbon monoxide gas, carbondioxide gas, nitrogen gas, ammonia gas, nitrous oxide gas, nitrogenoxide gas, nitrogen dioxide gas, oxygen gas, water vapor, fluorine gas,fluorine hydride gas, trifluoroalcohol, trifluorotoluene, hydrogensulfide, sulfur dioxide, carbon disulfide, and chlorine gas.

By choosing appropriately raw material gases incorporating metalelements and decomposition gases, it is possible to prepare varioustypes of metal carbides, metal nitrides, metal oxides, metal halides,and metal sulfides.

Discharge gases, which primarily tend to result in a plasma state, aremixed with the above reactive gases, and the resulting mixture isconveyed into a plasma discharge generator. Employed as such dischargegases are nitrogen gas and/or Group 18 elements in the periodic table,specifically helium, neon, argon, krypton, xenon, and radon. Of these,nitrogen, helium, and argon are preferably employed.

Film formation is carried out by blending the above discharge gases andthe reactive gases and feeding the resulting mixed gas into a plasmadischarge generator (being a plasma generator). The ratio of dischargegases to the reactive gases may vary depending on the properties of thefilm to be prepared. However, the reactive gases are supplied so thatthe ratio of the discharge gases is at least 50% with respect to theentire gas mixture.

FIG. 2 is a schematic view showing one example of an atmosphericpressure plasma discharge treatment apparatus which employs a system inwhich a substrate is treated between counter electrodes which are usefulfor the present invention.

The atmospheric pressure plasma discharge treatment apparatus accordingto the present invention is composed of at least plasma dischargetreatment apparatus 30, dual-power source incorporating electric fieldapplying means 40, gas supplying means 50, and electrode temperaturecontrolling means 60.

In FIG. 2, substrate F is subjected to plasma discharge treatment inspace (being the discharge space) 32 between counter electrodes composedof roller rotating electrode (first electrode) 35 and a group of squarecylindrical type fixed electrodes (second electrodes), resulting information of a thin film. In FIG. 2, a pair of a group of squarecylindrical electrodes (the second electrode) 36 and roller rotatingelectrode 35 (the first electrode) form one electric field and theresulting 1 unit form, for example, a low density layer. FIG. 2 shows anexample of the constitution in which the unit constituted as above isarranged at 5 positions. By independently controlling the type of rawmaterials and output voltage supplied by each of the units, it ispossible to continuously form a transparent gas barrier layer of thelaminated layer type specified in the present invention.

The following high frequency electric fields are applied to dischargespace 32 (the space between counter electrodes) between rotating rollerelectrode 35 (the first electrode) and square cylindrical type fixedelectrode group 36 (the second electrodes). A first high frequencyelectric field of frequency ω₁, electric field strength V₁ and electriccurrent I₁ is applied to rotating roller electrode (the first electrode)35 from first power source 41, while second high frequency electricfield of frequency ω₂, electric field strength V₂ and electric currentI₂ is applied to each of square cylindrical type electrodes group 36from each of the corresponding second power source 42.

First filter 43 is arranged between rotating roller electrode 35 (thefirst electrode) and first power source 41. First filter 43 is designedso that electric current from first power source 41 to the firstelectrode readily flows and electric current from second power source 42to the first power source barely flows while the electric current fromsecond power source 42 is grounded. Further, second filter 44 isarranged respectively between square cylindrical type electrode group 36(the second electrodes). Second filter 43 is designed so that electriccurrent from second power source 42 to the second electrode readilyflows and electric current from first power source 41 to the secondpower source barely flows while the electric current from first powersource 42 is grounded.

Further, in the present invention, rotating roller electrode 35 may beemployed as the second electrode, and square cylindrical fixed electrodegroup 36 may be employed as the first electrode. In either case, thefirst power source is connected to the first electrode, while the secondpower source is connected to the second electrode. It is preferable thatthe first electrode results in application of a higher high frequencyelectric field intensity than the second power source (namely V₁>V₂).Further, the possibility exists to result in ω₁<ω₂.

Further, it is preferable that electric current results in I₁<I₂.Electric current I₁ of the first high frequency electric field ispreferably 0.3-20 mA/cm², but is more preferably 1.0-20 mA/cm², whileelectric current I₂ of the second high frequency electric field ispreferably 10-100 mA/cm², but is more preferably 20-100 mA/cm².

Gas G generated by gas generator 51 of gas supply means 50 is subjectedto flow rate control and is introduced into plasma discharge treatmentvessel 31 from a gas supply inlet.

Substrate F is conveyed from a master roll (not shown) while beingunwound or conveyed from the previous process. It passes over guideroller 64 and is subjected to insulation of accompanied air by niproller 65. Subsequently, while brought into contact with roller rotatingelectrode 35 and being run around, it is conveyed between rotatingroller electrode 35 and square cylindrical fixed electrode group 36 andis subjected to application of the electric field from both rotatingroller electrode 35 (the first electrode) and square cylindrical fixedelectrode group 36 (the second electrodes), whereby discharge plasma isgenerated between facing electrodes 32 (in the discharge space).Substrate F is run around while brought in contact with rotating rollerelectrode 35 and results in formation of a thin film due to plasma stategas. Resulting substrate F is wound up after passing nip roller 66 andguide roller 67, employing a winder (not shown), or conveyed to the nextprocess.

Treatment exhaust gas G′ which has subjected to discharge treatment isdischarged from exhaust 53.

During formation of the above thin film, in order to heat or coolrotating roller electrode 35 (the first electrode) and squarecylindrical fixed electrode group 36 (the second electrodes), themedium, which has been subjected to temperature control via electrodetemperature control means 60, is conveyed to both types of electrodesvia piping 61 employing liquid conveying pump P, whereby temperature iscontrolled via the interior of the electrodes. Incidentally, 68 and 69are partitions which isolate plasma treatment vessel 31 from theexterior.

In the gas barrier layer according to the present invention, inorganiccompounds incorporated in the gas barrier layer are preferably SiO_(x),SiN_(x), or SiO_(x)N_(y) (where x is 1-2, while y is 0.1-1). In view ofwater permeability, light transmittance, and the atmospheric pressureplasma CVD adaptability, described below, they are preferably SiO_(x).

It is possible to combine, at a predetermined ratio, inorganic compoundsaccording to the present invention with the above organic siliconcompounds and further oxygen gas and nitrogen gas, and to prepare a filmincorporating at least an O atom or an N atom, and a Si atom. Further,SiO₂ exhibits relatively high transparency but relatively low gasbarrier properties due to permeation of some moisture, wherebyincorporation of N atoms is more preferred. Namely, when the ratio ofthe number of oxygen atoms to the number of nitrogen atoms is expressedby x:y, x/(x+y), the ratio is preferably at most 0.95, but is morepreferably at most 0.80. Accordingly, in the gas barrier layer accordingto the present invention, light transmittance T is preferably at least80%.

Further, when the ratio of N atoms increases, the resulting lighttransmittance decreases, whereby when x=0, the resulting color tends tobecome yellowish. Consequently, the specific ratio of oxygen atoms tonitrogen atoms may be determined depending on its use. For example, in adisplay device, in the use which requires higher light transmittancewhen a film is formed on the light emitting side of a light emittingelement, it is preferable that x/(x+y) is 0.4-0.95, since it is therebypossible to realize compatibility of light transmittance and waterresistance. Further, in the use in which light is preferably absorbed orshielded as for imaging inhibiting film arranged on the reverse side ofthe light emitting element of the display device, it is preferable thatx/(x+y) is 0-0.4.

Consequently, the gas barrier layer of the present invention ispreferably transparent. By making the above gas barrier layertransparent, it is possible to make the gas barrier film transparent,whereby it become to possible to apply organic EL elements totransparent substrates.

FIG. 1 is a schematic view showing one example of the layerconfiguration of the transparent gas barrier film according to thepresent invention, and the density profile thereof.

Transparent gas barrier film 1 according to the present inventionincorporates substrate 2, having thereon laminated layers which differin density. In the present invention, a feature is that medium densitylayer 4 according to the present invention is arranged between lowdensity layer 3 and high density layer 5. Further, medium density layer4 is arranged on the high density layer, and configuration composed ofthese low density layer, medium density layer, high density layer, andmedium density layer is designated as one unit. FIG. 1 shows an examplein which two such units are laminated. At the time, the densitydistribution in each of the density layers is controlled to be uniformand density change between adjacent layers becomes step-like. Further,in FIG. 1, medium density layer 4 is shown as a single layer but ifnecessary, may be composed of two layers.

<<Substrates>>

Substrates employed for the transparent gas barrier film according tothe present invention are not particularly limited as long as they arecomposed of organic materials capable of maintaining a gas barrier layerexhibiting the above barrier properties.

Specifically employed may be polyolefin (PO) resins such as ahomopolymer of ethylene, polypropylene, butane or a copolymer; amorphouspolyolefin resins (APO), polyester based resins such as polyethyleneterephthalate (PET), or polyethylene 2,6-naphthalate (PEN), polyamidebased (PA) resins such as nylon 6,nylon 12, or copolymer nylon,polyvinyl alcohol based resins such as polyvinyl alcohol (PVA) resins orethylene-vinyl alcohol copolymers (EVOH), polyimide resins (PI),polyetherimide (PEI) resins, polysulfone (PS) resins, polyethersulfone(PES) resins, polyether ketone (PEEK) resins, polycarbonate (PC) resins,polyvinyl butyral (PVB) resins, polyarylate (PAR) resins, as well asfluorine based resins such as ethylene-ethylene tetrafluoride copolymer(ETFE), ethylene trifluoride monochloride (PFA), ethylenetetrafluoride-perfluoroalkyl vinyl ether copolymer (FEP), vinylidenefluoride (PVDF), vinyl fluoride (PVF), or perfluorovinyl ether copolymer(EPA).

Further, other than the resins listed above, employed may bephotocurable resins such as resin compositions composed of acrylatecompounds incorporating radically reactive unsaturated compounds, resincompositions composed of the above acrylate compounds and mercaptocompounds having a thiol group, and resin compositions prepared bydissolving, in polyfunctional acrylate monomer, oligomers such asepoxyacrylate, urethane acrylate, polyester acrylate or polyetheracrylate, and mixtures thereof. Further, it is possible to employ, as asubstrate film, those which are prepared by laminating at least one ofthe above resins by means of lamination or coating.

These materials may be employed individually or appropriately blended.Of these, preferably employed are commercially available products suchas ZEONEX and ZEONOA (produced by Nippon Zeon Co., Ltd.), amorphouscyclopolyolefin resin film, ARTON (produced by JSR, Inc.), polycarbonatefilm, PUREACE (produced by TEIJIN Ltd.), cellulose acetate film, KONICAMINOLTA TAC KC4UX and KC8UX (produced by Konica Minolta Opto, Inc.).

Further, the substrate is preferably transparent. When a substrate andthe layers formed on the substrate are transparent, it is possible tomake the resulting gas barrier film transparent, whereby it is possibleto employ it as a transparent substrate of organic EL elements.

Still further, the substrate according to the present invention theemploying resins listed above may be an unstretched film or a stretchedfilm.

It is possible to produce the substrate according to the presentinvention employing common methods known in the art. For example,material resins are fused employing an extruder, extruded via aring-like die or a T-die, and rapidly cooled, whereby it is possible toproduce a substrate which is substantially amorphous, is not orientedand not stretched. Further, it is possible to produce a stretchedsubstrate in such a manner that an unstretched substrate is stretched inthe substrate traveling (longitudinal) direction or at a right angle(perpendicular) to the substrate conveying direction, employing methodsknown in the art, such as uniaxial stretching, tenter system sequentialbiaxial stretching, or tubular system simultaneous biaxial stretching.In such stretching, the stretching factor may be appropriately selectedmatched to the resins as a substrate material, but is preferably 2-10times in the longitudinal direction and the lateral direction.

Further, prior to forming a deposition film, the substrate according tothe present invention may be subjected to surface treatment such as acorona treatment, a flame treatment, a plasma treatment, aglow-discharge treatment, a surface-roughing treatment, or a chemicaltreatment.

Still further, to enhance adhesion to the deposition film, an anchorcoating layer may be formed on the surface of the substrate according tothe present invention. Anchor coating materials employed in the aboveanchor coating layer may include polyester resins, isocyanate resins,urethane resins, acrylic resins, ethylene vinyl alcohol resins, modifiedvinyl resins, epoxy resins, modified styrene resins, modified siliconeresins, and alkyl titanate. These may be employed individually or incombinations of at least two types. Additives known in the art may beadded to the above anchor coating agents. Further, the above anchorcoating materials may be applied onto a substrate, employing methodsknown in the art, such as roller coating, gravure coating, knifecoating, dip coating, or spray coating. Subsequently, solvents andthinners are removed via drying, whereby it is possible to form ananchor coating layer. The coated weight of the above anchor coatingagents is preferably about 0.1-about 5 g/m² (in the dry state).

As a substrate, a long-length product, which is wound into a roll, isconvenient. Further, the thickness of the film-like substrate employedin the present invention is preferably 10-200 μm, but is more preferably50-100 μm.

Since organic EL displays and highly detailed color liquid crystaldisplays require high water vapor barring properties, water vaporpermeability, determined by the JIS K 7129 method, is preferably at most1.0 g/m²/day. Further, when the organic EL display according to thepresent invention is applied to a display, water vapor permeability ispreferably less than 0.1 g/m²/day, since the display life is sometimesextremely shortened by formation of dark spots due to the presence of aminute amount of water vapor.

EXAMPLES

The present invention will now be described with reference to examples,however the present invention is not limited thereto.

Example 1 <<Preparation of Organic EL Element>> (Preparation of OrganicEL Element OLED1-1)

A transparent gas barrier film was prepared in such a manner that threeunits, each of which is composed of a low density layer, a mediumdensity layer, a high density layer, and another medium density layer inthat order are applied, onto a 100 μm thick polyethylene terephthalatefilm (produced by Teijin DuPont Ltd., and hereinafter referred to asPEN) under the following discharge conditions employing the followingatmospheric pressure plasma discharge treatment apparatus to result inthe density distribution profile shown in FIG. 1.

(Atmospheric Plasma Discharge Treatment Apparatus)

By employing the atmospheric plasma discharge treatment apparatusdescribed in FIG. 2, a roller electrode covered with dielectriccompounds and a set of plurality of square cylindrical electrodes wereprepared as follows.

The roller electrode employed as the first electrode was prepared asfollows. Titanium alloy T64 jacket roller metallic base material, havinga cooling means employing cooling water, was covered with a high densityand high adhesive alumina sprayed film to realize a roller diameter of1,000 mm. On the other hand, the square cylindrical electrode of thesecond electrode was prepared as follows. A hollow square cylindricaltitanium alloy T64 was covered with the same dielectrics as above at athickness of 1 mm under identical conditions, whereby a counter squarecylindrical fixed electrode group was prepared.

Regarding the rotating roller electrode, 24 of above square cylindricalelectrodes were arranged while 1 mm gap between the counter electrodeswas maintained. The total discharge area of the square cylindricalelectrode group was 150 cm (length in the lateral direction)×4 cm(length in the conveying direction)×24 (the number of electrodes) toequal 14,400 cm². Meanwhile, appropriate filters were arranged in eachcase.

During plasma discharge, the first electrode (the rotating rollerelectrode) and the second electrode (the square cylindrical fixedelectrode group) were subjected to temperature control at 80° C. and therotating roller electrode was driven to rotate, whereby a thin film wasformed. Of the above 24 square cylindrical electrodes, from the upstreamside, 4 electrodes were employed to form the first layer (Low DensityLayer 1) described below, the subsequent 6 electrodes were employed toform the 2nd layer (Medium Density Layer 1) described below, thefollowing 8 electrodes were employed to form the 3rd layer (High DensityLayer 1), and the remaining 6 electrodes were employed to form the 4thlayer (Medium Density Layer 1). Four layers were laminated in one pass,while setting each respective condition. Subsequently, the aboveconditions were repeated twice, whereby Transparent Gas Barrier Film 1was prepared.

(Discharge Conditions) (1st Layer: Low Density Layer 1)

Plasma discharge was carried out under the following conditions, wherebyabout 90 nm thick Low Density Layer 1 was formed.

<Gas Conditions> Discharge gas: nitrogen gas 94.8% by volume Thin layerforming gas: hexamethyldisiloxane  0.2% by volume (vaporized via avaporizer produced by Lintec Co., while blended with nitrogen gas)Additive gas: oxygen gas  5.0% by volume

<Power Source Conditions: only employed for the power source on thefirst electrode side> First electrode side: power source type, highfrequency power source produced by Oyo Electric Co., Ltd. Frequency 80kHz Output density 10 W/cm²

Density of the 1st layer (low density layer), prepared as above, wasdetermined via an X-ray reflectance method employing MXP21 produced byMAC Science Co., Ltd., resulting in 1.90.

(2nd Layer: Medium Density Layer 1)

Plasma discharge was carried out under the following conditions, wherebyabout 90 nm thick Medium Density Layer 1 was formed.

<Gas Conditions> Discharge gas: nitrogen gas 94.9% by volume Thin layerforming gas: hexamethyldisiloxane  0.1% by volume (vaporized via thevaporizer produced by Lintec Co., while blended with nitrogen gas)Additive gas: oxygen gas  5.0% by volume

<Power Source Conditions: employed only in the power source on the firstelectrode side> First electrode side, power source type, high frequencypower source produced by Oyo Electric Co., Ltd. Frequency 80 kHz Outputdensity 10 W/cm²

Density of the 2nd layer (low density layer), prepared as above, wasdetermined via an X-ray reflectance method employing MXP21 produced byMAC Science Co., Ltd., resulting in 2.05.

(3rd Layer: High Density Layer 1)

Plasma discharge was carried out under the following conditions, wherebyabout 90 nm thick High Density Layer 1 was formed.

<Gas Conditions> Discharge gas: nitrogen gas 94.9% by volume Thin layerforming gas: hexamethyldisiloxane  0.1% by volume (vaporized via thevaporizer produced by Lintec Co., while blended with nitrogen gas)Additive gas: oxygen gas  5.0% by volume

<Power Source Conditions> 1st electrode side, power source Type, highfrequency power source produced by Oyo Electric Co., Ltd. Frequency 80kHz Output density 10 W/cm² 2nd electrode side, power source type: highfrequency power source produced by Pearl Kogyo Co., Ltd. Frequency 13.56kHz Output density 10 W/cm²

Density of the 3rd layer (high density layer), prepared as above, wasdetermined via an X-ray reflectance method employing MXP21 produced byMAC Science Co., Ltd., resulting in 2.20.

(4th Layer: Medium Density Layer 2)

Medium Density Layer 2 was prepared under the same conditions as inabove 2nd layer (Medium Density Layer 1).

Water vapor transmission rate was determined employing the method basedon JIS K 7129B, resulting in at most 1.0×10⁻³ g/m², while the oxygentransmission rate was determined employing the method based on JIS K7126B, resulting in at most 1×10⁻³ g/m²/g.

(Preparation of ITO Substrate)

Subsequently, 120 nm thick ITO (indium tin oxide) film was formed on theabove gas barrier film substrate, followed by patterning. Thereafter,the resulting substrate provided with the above ITO transparentelectrode was subjected to ultrasonic cleaning via isopropyl alcohol,was dried via desiccated nitrogen gas, and was subjected to UV ozonecleaning for 5 minutes. The resulting substrate was fixed to thesubstrate holder of a commercially available vacuum evaporationapparatus followed by reduction of pressure to a vacuum degree of 4×10⁻⁴Pa, whereby ITO Substrate 100 was prepared.

(Formation of Positive Hole Transporting Layer)

Subsequently, as shown in FIG. 3, while ink-jet recording head 10 ismoving at a high rate with respect to ITP substrate 100, droplets D,incorporating Exemplified Compound B6, were deposited via dischargingfluid D incorporating Exemplified Compound B6 as a positive holetransporting material onto the upper surface of substrate 100. Thedeposited droplets (fluid D) exhibited a diameter of about several tensμm, and positive hole transporting layer 111 was formed via discharge ofa predetermined amount of fluid D. Subsequently, polymerization wasperformed under heating conditions at 200° C. for one hour, whereby athin polymer film was formed. The average molecular weight of theresulting polymer was approximately 10,000 (at a repeating unit of 16.6)and the film thickness was 50 nm.

(Formation of Electron Transporting Layer)

In the same manner as in the formation of the above positive holetransporting layer, fluid D incorporating Exemplified Compound B7 as aelectron transporting material was discharged onto substrate 100 havingpositive hole transporting layer 111 from ink-jet recording head 10,whereby droplets incorporating Exemplified Compound B7 were deposited.The deposited droplets exhibited a diameter of about several tens μm,and electron transporting layer 112 was formed via discharge of apredetermined amount of fluid. Further, polymerization was performedunder heating conditions at 200° C. for one hour, whereby a thin polymerfilm was formed. The average molecular weight of the resulting polymerwas approximately 20,000 (at a repeating unit of 40.5) and the filmthickness was 50 nm.

(Formation of Cathode)

A 200 nm thick layer of aluminum was deposited onto electrontransporting Layer 112, prepared as above, whereby cathode 113 wasformed.

(Sealing via Gas Barrier Film)

Sealing via gas barrier film 114 was carried out in such a manner thatthe side forming a gas barrier film was sealed while being opposed witha cathode, whereby Organic Element OLED 1-1 of the present invention wasformed. When 20 V voltage was applied to resulting Organic Element OLED1-1, employing the ITO side as positive and the aluminum side asnegative, green light emission at a peak wavelength of 500 nm wasobserved.

(Preparation of Organic Element OLED2-1)

Organic EL Element 2-1 was prepared in the same manner as above OrganicEL Element 1-1, except that the constitution of the positive holetransporting layer and the electron transporting layer was changed asfollows.

(Formation of Positive Hole Transporting Layer)

Fluid D, incorporating Exemplified Compound A7 as a positive holetransporting material and dodecylmercaptan (at a mol ratio of 10:1), wasdischarged onto the upper surface of substrate 100, whereby positivehole transporting layer 111 was formed. Subsequently, polymerization wasperformed under heating conditions at 200° C. for one hour, whereby athin polymer film was formed. The average molecular weight of theresulting polymer was approximately 50,000 (at a repeating unit of 9.2)and the film thickness was 50 nm.

(Formation of Electron Transporting Layer)

Fluid D, incorporating Exemplified Compound A12 as an electrontransporting material and octadecyl alcohol (at a mol ratio of 10:1),was discharged onto the upper surface of substrate 100, whereby electrontransporting layer 112 was formed. Subsequently, polymerization wasperformed under heating conditions at 200° C. for one hour, whereby athin polymer film was formed. The average molecular weight of theresulting polymer was approximately 4,000 (at a repeating unit of 8.0)and the film thickness was 50 nm.

(Preparation of Organic EL Element OLED3-1)

Organic EL Element OLED3-1 of the present invention was prepared in thesame manner as above Organic EL Element OLED1-1, except thatconstitutions of the positive hole transporting layer and the electrontransporting layer were changed as follows.

By employing the same method as above, α-NPD was applied onto the ITOsubstrate at a 50 nm film thickness to form a positive hole transportinglayer. After drying the resulting coating at 100° C. for 30 minutes,Alg₃ as an electron transporting material was applied at a thickness of50 nm, and the resulting coating was dried in the same manner as above.Subsequently, 0.5 nm thick LiF and 110 nm thick Al each were depositedto form a cathode, whereby Comparative Organic EL Element OLED3-1 wasprepared.

(Preparation of Organic El Element 4-1)

Organic El Element 4-1 of the present invention was prepared in the samemanner as above Organic EL element OLED1-1, except that theconstitutions of the positive hole transporting layer and the electrontransporting layer were changed as follows.

Positive hole transporting layer 111 was formed by discharging, ontosubstrate 100, fluid D incorporating Exemplified Compound B6 as apositive hole transporting material. Subsequently, polymerization wascarried out under conditions of an exposure electron current of 5 mA andelectron exposure energy of −50 eV, whereby a thin polymer film wasformed. The average molecular weight of the formed polymer wasapproximately 18,000 (at a repeating unit of 30.0) and the filmthickness was 50 nm.

Fluid D, incorporating Exemplified Compound D8 as a electrontransporting material, was discharged in the same manner as above ontothe upper surface of substrate 100, whereby electron transporting layer112 was formed. The average molecular weight of the formed polymer wasapproximately 15,000 (at a repeating unit of 28.3) and the filmthickness was 50 nm. Further, after sealing, the degree ofpolymerization was enhanced by applying, to the above element, electriccurrent of a current density of 50 mA/cm².

<<Evaluation of Organic EL Elements>>

Each of the organic EL elements, prepared as above, was evaluated foreach characteristic employing the following methods. Table 1 shows theresults.

(Evaluation of Light Emission Luminance)

Organic EL Element OLED3-1 resulted in a flow of electric current at aninitial driving voltage of 4 V, whereby it resulted in green lightemission. With regard to Organic EL Elements OLED1-1 and OLED2-1, lightemission luminance (cd/m²) and light emission efficiency (in lm/W) weredetermined when 10 V direct current voltage was applied at 23° C. Theabove light emission luminance and the light emission efficiency eachwere expressed as a relative value when each value of Organic EL ElementOLED3-1 was 100. The light emission luminance was determined employing aspectroradioluminance meter CS-1000 (produced by Konica Minolta Sensing,Inc.).

(Evaluation of Durability)

During driving each organic EL element employing a constant electriccurrent of 10 mA/cm², a half-life period, which passed until the initialluminance decreased to one half, was determined and the resulting valuewas employed as an index of durability. The half-life period wasexpressed as a relative value when the value of Organic EL Element OLED3-1 was 100.

Further, after 20-hour drive at a constant electric current of 10mA/cm², the number of visually noticeable non-light emitting points(dark spots) was determined in an area of 2 mm×2 mm.

TABLE 1 Organic Light EL Emission Half-Life Number of Element LuminancePeriod Dark Spots Remarks OLED1-1 110 140 7 Present Invention OLED2-1106 135 9 Present Invention OLED3-1 100 100 60 Comparative ExampleOLED4-1 109 138 8 Present Invention

As can clearly be seen from Table 1, the organic EL elements,constituted as specified by the present invention, resulted in a markeddecrease in dark spots and enhancement in half-life period. Further,enhancement in luminance was noted.

Example 2 <<Preparation of Organic EL Elements>>

Under the same conditions as those which were employed to prepareOrganic EL Element OLED1-1 described in Example 1, Organic EL ElementsOLED5-1-3 were prepared, which were composed of materials and resultedin the film thickness described in Table 2 below. Further, under thesame conditions as those which were employed to prepare Organic ELElement OLED2-1, Organic EL Elements OLED5-4-6, were prepared which werecomposed of materials and resulted in the film thickness, described inTable 2 below. Still further, under the same conditions as those whichwere employed to prepare Organic EL Element OLED3-1, Comparative OrganicEL element OLED5-7 was prepared, which was composed of materials andresulted in the film thickness, described in Table 2 below.

TABLE 2

Positive Hole Electron Transporting Layer Transporting (50 nm) LightEmitting Layer (50 nm) Layer (50 nm) Cathode Organic Repeat- Repeat-Repeat- (100 nm) EL Con- ing Host Dopant ing Con- ing Con- Re- Elementstituent Unit Material (5 mol %) Unit stituent Unit stituent marksOLED5-1 B16 45.0 B13 Ir-12 35.0 BCP — A1 Inv. OLED5-2 B16 55.5 B17 D-134.5 B30 43.2 A1 Inv. OLED5-3 B16 77.5 B17 Ir-12 62.2 B28 60.5 A1 Inv.OLED5-4 A7 + C₈H₁₇SH  8.5 A15 Ir-12 + C₈H₁₇SH  8.0 BCP — A1 Inv. OLED5-5A7 + C₁₂H₂₅OH  7.8 A13 D-1 + C₁₂H₂₅OH  7.7 A12  8.0 A1 Inv. OLED5-6A16 + C₁₄H₂₉Br  9.5 A14 D-1 + C₁₄H₂₉Br  9.0 A18  9.0 A1 Inv. OLED5-7α-NPD — CBP Ir-12 — BCP — A1 Comp. Inv.: Present Invention, Comp.:Comparative Example

<<Evaluation of Organic EL Elements>>

Organic EL Elements OLED5-1-7 were evaluated for each characteristicemploying the same methods described in Example 1. Table 3 shows theresults.

TABLE 3 Organic Light Number EL Emission Half-Life of Dark ElementLuminance Period Spots Remarks OLED5-1 107 120 10 Present InventionOLED5-2 112 135 6 Present Invention OLEDS-3 113 140 7 Present InventionOLED5-4 104 118 14 Present Invention OLED5-5 108 128 13 PresentInvention OLED5-6 109 130 11 Present Invention OLED5-7 100 100 75Comparative Example

As can clearly be seen from the results of Table 3, of phosphorescenceemitting type organic EL elements, the organic EL elements composed asspecified by the present invention resulted in higher light emissionluminance, exhibited longer life, minimized formation of dark spots, andexhibited higher durability, compared to the Comparative Example.

Further, Organic EL Element OLED5-3, in which a compound having apolymerizable group and another compound having a reactive group wereemployed in combination, exhibited higher durability than Organic ELElement OLED5-1 in which the compound having a reactive group wasemployed as an electron transporting material and resulted in the samedurability enhancing effects as Organic EL Element OLED5-2.Consequently, it is preferable that in at least some portion near theinterface of the light emitting layer and the electron transportinglayer, a covalent bond is formed.

Example 3

Organic EL Element 5-2 prepared in Example 2, a green light emittingorganic EL element which was prepared in the same manner as Organic ELElement OLED5-2 of the present invention prepared in Example 2, exceptthat the phosphorescent compound was replaced with Exemplified CompoundIr-1, and a red light emitting organic El element which was prepared inthe same manner as Organic EL Element OLED5-2 of the present invention,except that the phosphorescent compound was replaced with ExemplifiedCompound Ir-9, were arranged on the same substrate, whereby the activematrix system full-color display device was prepared. In FIG. 5, onlyshown is the schematic view of display section A of the preparedfull-color display device. Namely, on the same substrate, provided are awiring section incorporating a plurality of scanning lines 205 and datalines 206, and a plurality of pixels 203 (such as pixels which emitlight in the red, green or blue region). Scanning lines 205 and aplurality of data lines 206 are each composed of conductive materials.Scanning lines 205 and data lines 206 intersect lattice-like at rightangles to one another and connect to pixel 203 at each intersection atright angles (details of which are not shown in the figure). The aboveplurality of pixels 3 is driven via the active matrix system providedwith organic El elements corresponding to each of the emitted lightcolors and each of the switching transistors and driving transistors asan active element. When scanning signals are applied from scanning lines205, image data signals are received from data lines 206 and light isemitted depending on the received image data. By appropriately arrangingeach of the red, green and blue pixels as described above, it ispossible to achieve a full-color display. Further, by driving thefull-color display device, bright and clear full-color moving images areproduced.

Example 4 <<Preparation of Lighting Device>>

The non-light emitting surface of each of the organic EL elements, whichemit individually blue light, green light, or red light, prepared inExample 3, was covered with a glass case, whereby a lighting device wasprepared. It is possible to employ the resulting lighting device as athin white light emitting lighting device which resulted in high lightemission efficiency and long life. FIG. 6 is a schematic view of thelighting device, while FIG. 7 is a sectional view of the lightingdevice. Organic EL Element 301 was covered with glass cover 302. Numeral305 is a cathode, 306 is an organic EL layer, and 307 is a glasssubstrate provided with a transparent electrode. Further, the interiorof glass cover 302 is filled with nitrogen gas 308, and water catchingagent 309 is provided.

Subsequently, color reproduction range during combination withcommercially available filters for display was evaluated. In combinationof organic EL elements with color filters, it was confirmed that thecolor reproduction range was broad and excellent performance wasrealized in color reproduction.

1. An organic electroluminescence element comprising a substrate having thereon an anode, a cathode and a plurality of organic layers between the anode and the cathode, wherein a first organic layer is provided by coating: a first oligomer compound made of 2 to 10 repeating units and having at least one polymerizable unit, or a first compound having one reactive group, followed by polymerization, and a second organic layer is stacked on the first organic layer, wherein the second layer is provided by coating: a second oligomer compound made of 2 to 10 repeating units and having at least one polymerizable unit, or a second compound having one reactive group, followed by polymerization, provided that a portion of an interface between the first organic layer and the second layer is bonded through a covalent bond.
 2. The organic electroluminescence element of claim 1, wherein the polymerizable group in the compound is a vinyl group.
 3. The organic electroluminescence element of claim 1, wherein the coating of the first organic layer is carried out by employing an ink-jet recording method.
 4. The organic electroluminescence element of claim 1, wherein the polymerization is carried out via exposure to an energy ray.
 5. The organic electroluminescence element of claim 4, wherein the energy ray is one selected from the group consisting of a ultraviolet ray, an electron beam, an ion beam, a heat ray, a radical beam and a radioactive ray.
 6. The organic electroluminescence element of claim 1, wherein the organic compound contained in the first organic layer is an aromatic compound having a tertiary amine group; and the compound contained in the second organic layer is a compound having an organic metal complex structure.
 7. The organic electroluminescence element of claim 1 further comprising a phosphorescent compound in the first organic layer or in the second organic layer.
 8. The organic electroluminescence element of claim 1, wherein the first organic layer is an electron transporting layer and the second organic layer is a positive hole transporting layer.
 9. The organic electroluminescence element of claim 1, wherein the repeating unit in the first oligomer compound and the second oligomer compound is derived from at least one selected from the group consisting of:


10. The organic electroluminescence element of claim 1, wherein the substrate is a transparent gas barrier film.
 11. The organic electroluminescence element of claim 1, wherein the organic electroluminescence element emits a white light.
 12. A display device comprising the organic electroluminescence element of claim
 11. 13. A lighting device comprising the electroluminescence element of claim
 11. 14. A display device comprising: a liquid crystal element as a display means; and the lighting device of claim
 14. 